Is anyone on here keeping koi betta fish? Thats what I'm thinking of keeping if I can find a nice one. Is anyone on here breeding any? Have striking betta( male or females)

If I set up a 30 gallon how many female betta to male if I decide to just do betta? I was thinking neons possibly as well. It's kind of odd but you ask me anything marine and I have a vast knowledge but FW, I was too much a water snob to care ha-ha so input would be nice. I am hoping to have a really nice planted setup thats very green and calm as an off set to my marine tanks. It's looking like it's the 30 gallon unless I luck out on a 4ft for cheap.